With the use of any form of electrical appliance, there is a need to electrically insulate conductors. With the push to continuously reduce in size and streamline all things electrical, there is a corresponding need to find better and more condensed insulators.
Epoxy resins have been used extensively in electrical insulators due to their practical benefit of being tough and flexible electrical insulators that can be easily adhered to surfaces. Traditional electrical insulators, such as mica or glass fibers, can be surface coated with these epoxy resins, which increases the material's strength, chemical resistance and electrically insulating properties.
Good electrical insulators, by their very nature, also tend to be good thermal insulators, which is not a desired effect. Thermal insulation, particularly for air-cooled electrical components, reduces the efficiency and durability of the components as well as the unit as a whole. It is desirable to produce insulators, such as groundwall insulators, having maximum electrical insulation while minimizing thermal insulation.
Improvements in epoxy resins have recently been made by using liquid crystal polymers. By mixing an epoxy resin with a liquid crystal polymer, a liquid crystal thermoset (LCT) epoxy resin is produced that contains polymers or monomers that have cross-linked properties and have significantly improved mechanical properties. See U.S. Pat. No. 5,904,984, which is incorporated herein by reference. A further benefit of LCTs is that they also have improved thermal conductivity over standard epoxy resins.
What makes LCT epoxy resins even more appealing is that they are also better able to conduct heat than a standard epoxy resin. U.S. Pat. No. 6,261,481, which is incorporated herein by reference, teaches that LCT epoxy resins can be produced with a thermal conductivity greater than that of conventional epoxy resins. For example, a standard Bisphenol A epoxy is shown to have thermal conductivity values of 0.18 to 0.24 watts per meter degree Kelvin (W/mK) in both the transverse (plane) and thickness direction. By contrast, an LCT epoxy resin is shown to have a thermal conductivity value, when used in practical applications, of no more than 0.4 W/mK in the transverse direction and no more than 0.9 W/mK in the thickness direction. However, the LCT epoxy resin lacks some physical properties, such as thermal stability and impregnating qualities.
Though these efforts benefit the art of electrical insulation, the field would benefit even more from the ability to transfer heat, without reducing the desired physical characteristics of the insulators. What is needed is an improved LCT epoxy resin, that has a greater thermal conductivity, but that does not compromise on electrical insulation or other structural integrities.